The Edinburgh Masker, popular in the 1980s, helped many stutterers improve their speech over time, until they no longer needed the device. Other stutterers found that the device "wore off" and became ineffective. Still other stutterers have used the device for more than twenty years with no carryover or "wearing off." No research investigated why the device had different effects on different people. Hypothetically, the users who developed carryover fluency may have used the device to help them overcome fears and anxieties, or they may have used the device to enhance stuttering therapy. For the users who experienced "wearing off," the device may have made these users talk louder, which increased vocal fold tension, and some users habituated to speaking with too-tense vocal folds.